1. Field of the Invention
The present invention relates to a tobacco smoke filter suitable for use in cigarettes, pipes, cigarette holders, and cigar holders, more particularly, to a tobacco smoke filter having improved filtering performance by using acetate filaments with a specific cross section as filter fibers.
2. Description of the Prior Art
Tobacco smoke contains aldehydes such as acetaldehyde, formaldehyde and acrolein, ketones such as acetone and phenolic compounds, which cause a bad influence on the tobacco taste or flavor. The tobacco smoke also contains alkaloids such as nicotine, organic acids and benzopyrene generally referred to as tar. It is well known that these substances are injurious to the smoker's health because they put loads on his lung, liver, kidney and stomach.
Various attempts have been made to remove these injurious tobacco components without impairing the tobacco taste or flavor, but none has been found completely satisfactory. A filter made of a tow of cellulose acetate filaments is in common use and in most cases, the filaments have a regular cross section (a) or an I-shape (b) or a Y-shape (c) produced by spinning through a spinneret (FIG. 1). The last two patterns are more often used because of their greater filtering ability, but on the other hand, filters using filaments having I-shape or Y-shape impair the tobacco flavor. Filters using filaments having a regular cross section are more effective in retaining the tobacco flavor or taste but, for the same filling density (the number of filaments with which a specific filter is filled), they have a lower pressure drop and less removal of tar and nicotine than filters using filaments having an I-shape or Y-shaped cross section.
Therefore, the present inventors have made various studies on the shape of the cross section of cellulose acetate filaments composing tobacco smoke filters so as to produce filters capable of very efficient removal of tars, nicotine and other injurious materials from tobacco smoke with less impairment of the tobacco flavor. As a result, the inventors have found that a filter made of cellulose acetate fibers having a C-shaped cross section has great ability to remove nicotine and tars without impairing the tobacco flavor and can be manufactured on an industrial scale.